Anyone who's ever tried eating treats under the very watchful eyes of their pet will understand the struggle. It's very hard to resist those puppy dog eyes, or that hangry cat waiting eagerly for their share (and probably drooling a little at the mouth).

It can be all too tempting to break off a bit of that chocolate bar, or scrape those leftovers into their bowl, but you're potentially doing them a lot more harm than good.

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We spoke to John Burns, veterinary surgeon and owner of Burns Pet Nutrition, to find out which human foods could be harmful to our pets and why.

1. Chocolate

"Although many people know this is toxic to dogs, they don't realise it can also affect cats," John explains. "Chocolate contains theobromine and while humans can easily break this down, dogs and cats struggle to do so, leading to toxic levels. Dark chocolate is the worst as it contains higher levels of theobromine." Depending on the quantity eaten and the size of your pet, it can cause vomiting and diarrhoea, increased heart rate and seizures.

We may love flavouring our foods with them, but they are toxic to dogs and even more so to cats. They can damage red blood cells, causing gastrointestinal irritation, anaemia and, in severe cases, organ damage and even failure. "Garlic is considered to be five times more toxic to dogs and cats than onions, and certain breeds (particularly those originating from Japan) are more susceptible," says John. "The symptoms of garlic and onion poisoning can be delayed and may not show for several days."

3. Grapes and raisins

John says grapes and raisins are "particularly toxic to dogs, but cats and ferrets are also susceptible. Even if a dog only eats a small amount, it can cause kidney failure."

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4. Macadamianuts

"These are very toxic to dogs although the reason why is not fully understood," John says. They can cause weakness, depression, vomiting, tremors, and/or hyperthermia. Most symptoms will pass within 12-48 hours.

5. Xylitol

"This is a sweetener often used in 'sugar –free' foods and is highly toxic to dogs," John explains. "Xylitol tricks the dog's body into thinking they have eaten something high in sugar and they produce lots of insulin causing their blood sugar level to drop dangerously low."

6. Foods high in salt and fat

Much like us, salty and fatty foods are not good for your pets. Foods high in salt "are likely to make your dog or cat thirsty if it is just a one-off," John says. "However if you regularly feed your dog foods high in salt it can lead to heart and blood pressure problems."

He also advises against fatty foods like bacon: "Although not toxic to dogs, eating something high in fat such as bacon can lead to pancreatitis - a painful and dangerous condition in dogs which can be fatal."

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7. Bones

Yes, be wary of giving a dog a bone. "Cooked bones are dangerous to dogs and cats as they can splinter. Raw bones can be given to dogs but it is best to do your research before feeding them these," John tells us.

8. Milk and dairy products

It's important to be aware that dairy products may give some dogs an upset stomach. "Some dogs are lactose intolerant so struggle to digest dairy and it can lead to digestive problems," says John.

9. Avocados

"These are only mildly toxic to dogs and cats but can have more a severe effect on birds and rabbits," John explains.

What to do if your pet does ingest anything harmful

So what happens if you stepped out of the room for a second and your dog or cat has somehow managed to consume half a box of chocolates in your absence?

John advises: "If you think your pet has eaten anything harmful it is always best to make contact with your vet immediately. Let the vet know what they have eaten and how much. They will be able to inform you if you need to take them for treatment or let you know of any symptoms to watch out for."

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To help ensure your pet gets the treatment they need in the event of illness, check out the range of pet insurance plans available from Petplan insurance. Having a plan like this in place can help ensure your pet is covered for any unexpected trips to the vet.

Are there healthy treats for pets?

As for healthy alternatives to keep those puppy dog (or hungry cat) eyes at bay, John cautions: "Pets don't necessarily need treats; it is us owners that love to give them. They can come in handy when training a dog or as a snack if you have a particularly greedy dog! Most vegetables are great to give as extras, broccoli and green beans are both a great source of vitamin C and fibre. Carrots are a great source of vitamin A and are also good to give frozen to teething puppies.

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"For cats, it is best to give lean meat, but they will then need a bit less food to ensure they don't have too much over the day. You could set aside part of your dog or cat's daily allowance of food and use these as treats to make sure they are not over-eating."

John adds: "As a general rule, all treats should be given in moderation." Now where have we heard that before?

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